Marie Fontaine

A passive polarization converter free of longitudinally-periodic structure

Based on an interpretation of the operating principle of passive polarization converters in terms of rotated vectorial eigenstates, it is shown that polarization rotation effects in angled facet passive converters can be maximized. Optimization of structure design achieves a device free of longitudinally-periodic structure with a very short converting length and low losses. Performance superior to any passive polarization converter reported in the literature is predicted for the device modeled with a vectorial numerical approach based on a finite-element scheme.

Analysis of arrow waveguides

Abstract The dispersion equation for ARROW (anti-resonant reflecting optical waveguide) and quasi-ARROW waveguides is derived using the equivalent transmission-line and transverse resonance method. The equation is reduced to a very simple form when the parameters of the ARROW waveguide are optimum. The propagation constant obtained from the dispersion and the simplified equation agree very well even in cases when the parameters of the ARROW waveguide vary away from the optimum values. The approach provides a powerful tool for analysis and design of ARROW waveguides.

Nonlinear self-phase-modulation effects: a vectorial first-order perturbation approach

A full-vectorial integral expression is derived to compute the effective mode area of any Kerr-type nonlinearoptical waveguide working in a self-phase-modulation regime. In order to highlight the correction brought by the vectorial approach in a strong guidance situation, we compare the effective area of a tapered fiber computed by the usual scalar expression with the one obtained with the full-vectorial approach.

Computations of optical birefringence characteristics of highly eccentric elliptical core fibers under various thermal stress conditions

The birefringence characteristics of optical fibers with a highly eccentric elliptical core are investigated under various thermal stress conditions. A new numerical method for solving the vectorial Maxwell equations is proposed which simultaneously takes into account the effects of ambient temperature and the geometrical distribution of the refractive indices of anisotropic propagation media. To verify the reliability of our numerical procedure, the birefringence characteristics are investigated of a highly birefringent elliptical core fiber used recently in the design of an optical sensor. The birefringence characteristics calculated by this procedure and those obtained from models currently used in the field of fiber‐optic sensing devices are compared with experimental data. For highly birefringent fibers, the numerical method proposed is far more accurate.

Scaling rules for nonlinear thin film optical waveguides

A mode power measure is applied to characterize nonlinear thin film optical waveguides in an approach analogous to that of Chelkowski and Chrostowski. Together with the normalized film thickness and the asymmetry coefficient, it allows us to get a concise overview of the waveguiding properties at a given power. For self-focusing film, we discuss the design conditions under which the degree of asymmetry significantly affects the waveguiding properties.

Nonlinear modal parameters of optical fibers: a full-vectorial approach

Nonlinear propagation constants and related nonlinearity coefficients of the fundamental modes of tapered fibers and step-index elliptical-core fibers are determined by the use of a new numerical approach for solving vectorial Maxwell’s equations, assuming a Kerr-type nonlinearity. A numerical method based on a finite-element scheme and the iteration procedure are reported. Nonlinear modal parameters computed from solutions of the scalar Helmholtz equation and vectorial Maxwell’s equations are compared with those obtained by the use of scalar and vectorial first-order perturbation methods. For both devices, the limitation of the scalar approach is clearly demonstrated. For tapered nonlinear fibers, the validity of the full-vectorial first-order perturbation method for some ranges of the input power is established. Physical interpretation of the results and their potential applications are given.

Cross-phase modulation phenomena in strongly guiding waveguides: a theoretical approach revisited

The theoretical approach recently proposed for investigating cross-phase modulation phenomena in weakly guiding waveguides with an arbitrary cross section is revisited. The unidirectional propagation equation is reformulated so that it becomes possible to precisely investigate the evolution of the polarization state in both weakly and strongly guiding devices. For [100]-oriented AlGaAs asymmetric waveguides, it is seen that interaction between the linear and nonlinear birefringences depends on the relative position of the slow axis of the device with respect to the 45° polarization-maintaining axis in the bulk medium. The design of an AlGaAs active polarization converter with a length of 3 cm and an effective area of ∼6 μm2 and that enables a quasi-total TE–TM conversion when using a peak power of 63 W is proposed.

A new numerical method for computing the optical characteristics of birefringent fibers

In this article, we present a new numerical method for solving vectorial Maxwell equations which makes it possible to study the birefringence of any geometric pattern of isotropic optical fiber. The distinguishing feature of this method is its use of an iterative process to determine the modes of propagation. The major advantage is the ease of the procedure since the various mathematical steps required can be performed by commercially available software.

Theoretical approach to investigating cross-phase modulation phenomena in waveguides with arbitrary cross sections

A novel approach, based on a scalar-corrected formalism, is proposed for investigating cross-phase modulation phenomena in waveguides with arbitrary cross sections. The proposed approach is applied to investigate the evolution of the polarization state in asymmetric angle-facet AlGaAs rib waveguides. It is seen that the orientation of the optical axes of the waveguides should be a determining parameter in optimizing the power transfer between the polarization modes and that asymmetric angle-facet AlGaAs rib waveguides could be promising devices for application in all-optical switching.

Universal dispersion and power curves for transverse magnetic waves propagating in slab waveguides with a nonlinear self‐focusing substrate

For TM‐polarized waves, a mode‐power measure is applied to characterize optical waveguides with a nonlinear self‐focusing substrate, producing a concise overview of the waveguiding properties at a given power for various designs. We also show how birefringence varies between the TE and TM modes as a function of the total power carried by the waveguide. Since our description is based on universal parameters, our results are applicable to different geometries of waveguide through simple scaling rules.